The invention may be embodied in still picture cameras, motion picture cameras, video-recorders, and other conventional image registration devices. Image registration devices embodying the invention can find immediate independent application in a wide range of systems, including automatic counters with laser light read-out systems (i.e., bar code scanners), computer systems with optical disk memory, audio and video optical disk players, night-vision devices, and laser microphones.
Throughout the specification, including in the claims, the phrase "image registration device" is employed to denote not only devices for imaging a time-invariant image (i.e., cameras), but also devices for imaging the output of spatial modulators which modulate a beam in a time-varying fashion (i.e., motion picture projectors).
The inventor has explained the application of homodyne methods to temporal carriers in the articles "Study of a Homodyne Photometer with Phase Modulation," Optics & Spectrosc., Vol. 49, No. 4, Oct. 1980, pp. 443-447, and "Signal Discrimination and Detection in the Presence of Nonadditive Noise," Optics & Spectrosc., May 1972, pp. 536-538. Similar homodyne methods are applied in the present invention to spatial carriers.